Re: Should __FD_SETSIZE still be set to 1024 ?

[Dag Wieers]

On Sat, 23 Jun 2001, Chris Wedgwood wrote:

> On Fri, Jun 22, 2001 at 04:59:36PM +0200, Dag Wieers wrote:
>
>     Is there a reason for __FD_SETSIZE to be 1024 in
>     linux/posix_types.h and gnu/types.h ?
>     Why can't we increase this number by default ?
>
> It might break stuff, like things that link with code that assumes it
> is only 1024.

So if someone wants to increase it for an application he needs to be sure
that everything that it is linked with is compiled with a similar
__FD_SETSIZE ?

Why can you safely increase the value in Squid then ?

>     Shouldn't it be set to the real limit of the kernel ?
>
> Nah... the kernel limit is 1024^2 --- you don't want to use select
> anywhere near that.

Yes, but still, why 1024 ?

>     (And let applications define their own limit if there is a need
>     for one ?)
>
> Well, squid and friends do this anyhow.

No, squid takes the lowest of both (FD_SETSIZE and SQUID_MAXFD) in main.c.
And the Squid configure gets the FD_SETSIZE value from linux/posix_types.h
;(

> Not only that, using a greatly increased value should be a run-time
> decision, lest you want your code to break on early 2.2.x kernels and
> before.

I'm still not convinced that something might break, since everybody
advices to increase __FD_SETSIZE before compiling Squid.

And if linux/posix_types.h defines the limit of open file descriptors of
the system, 1024 is (IMO) a wrong number. But then again, nobody bothered
to change it...

Thanks for your respons.

--   dag wieers,  [e-mail],  http://dag.wieers.com/   --
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